Chemical synthesis hydrolysis

Catalysts for Fine Chemical Synthesis Hydrolysis, Oxidation and Reduction. Volume 1... 

Other possible chemical synthesis routes for lactic acid include base-cataly2ed degradation of sugars oxidation of propylene glycol reaction of acetaldehyde, carbon monoxide, and water at elevated temperatures and pressures hydrolysis of chloropropionic acid (prepared by chlorination of propionic acid) nitric acid oxidation of propylene etc. None of these routes has led to a technically and economically viable process (6). 

Hexanedione [110-13-4] (acetonylacetone) is one of the most widely used 1,4-diketones. It is a colorless high boiling Hquid prepared by the hydrolysis of 2,5-dimethylfuran (332,333), by oxidation of 2,5-hexanediol (334) or 5-hexen-l-one (335), and from allylacetone (336). Its main use is in solvent systems and as a raw material for chemical synthesis. It is reportedly not highly toxic (336). 

Enzymatic hydrolysis of A/-acylamino acids by amino acylase and amino acid esters by Hpase or carboxy esterase (70) is one kind of kinetic resolution. Kinetic resolution is found in chemical synthesis such as by epoxidation of racemic allyl alcohol and asymmetric hydrogenation (71). New routes for amino acid manufacturing are anticipated. 

Chemical Synthesis. The first synthesis of ascorbic acid was reported ia 1933 by Reichsteia and co-workers (14,39—42) (Fig. 4). Similar, iadependent reports pubHshed by Haworth and co-workers followed shordy after this work (13,43—45). L-Xylose (16) was converted by way of its osazone (17) iato L-xylosone (18), which reacted with hydrogen cyanide forming L-xylonitfile (19). L-Xylonitfile cyclized under mild conditions to the cycloimine of L-ascorbic acid. Hydrolysis of the cycloimine yielded L-ascorbic acid. The yield for the conversion of L-xylosone to L-ascorbic acid was ca 40%. 

It is well known that the 1-phosphates of the ketoses, L-fuculose (51) and L-rhamnulose (52) have considerable biochemical interest. Their chemical synthesis has not been described as far as is known to the writer, but the rate of acid hydrolysis of L-fuculose 1-phosphate, obtained by enzymatic synthesis, has been determined by Heath and Ghalambor (20) and that of L-rhamnulose 1-phosphate by H. Sawada (48) and by Chiu and Feingold (II). They found that the rate of... 

D-Pantolactone and L-pantolactone are used as chiral intermediates in chemical synthesis, whereas pantoic acid is used as a vitamin B2 complex. All can be obtained from racemic mixtures by consecutive enzymatic hydrolysis and extraction. Subsequently, the desired hydrolysed enantiomer is lactonized, extracted and crystallized (Figure 4.6). The nondesired enantiomer is reracemized and recycled into the plug-flow reactor [33,34]. Herewith, a conversion of 90-95% is reached, meaning that the resolution of racemic mixtures is an alternative to a possible chiral synthesis. The applied y-lactonase from Fusarium oxysporum in the form of resting whole cells immobilized in calcium alginate beads retains more than 90% of its initial activity even after 180 days of continuous use. The biotransformation yielding D-pantolactone in a fixed-bed reactor skips several steps here that are necessary in the chemical resolution. Hence, the illustrated process carried out by Fuji Chemical Industries Co., Ltd is an elegant way for resolution of racemic mixtures. 

Hydrolysis, oxidation, and reduction / edited by Stan M. Roberts and Geraldine Poignant, p. cm—(Catalysts for fine chemical synthesis v. 1)... 

Table III summarizes the parameters that affect Brrfnsted acid-catalyzed surface reactions. The range of reaction conditions investigated varies widely, from extreme dehydration at high temperatures in studies on the use of clay minerals as industrial catalysts, to fully saturated at ambient temperatures. Table IV lists reactions that have been shown or suggested to be promoted by Br nsted acidity of clay mineral surfaces along with representative examples. Studies have been concerned with the hydrolysis of organophosphate pesticides (70-72), triazines (73), or chemicals which specifically probe neutral, acid-, and base-catalyzed hydrolysis (74). Other reactions have been studied in the context of diagenesis or catagenesis of biological markers (22-24) or of chemical synthesis using clays as the catalysts (34, 36). Mechanistic interpretations of such reactions can be found in the comprehensive review by Solomon and Hawthorne (37).

A conceptually similar approach applied in an industrial process is described by the Bristol—Myers—Squibb group, who required l-6-OH norleucine as an intermediate in the synthesis of their drug Omapatrilat. T o avoid a lengthy chemical synthesis of the oxoacid, it was more convenient to start with the racemic amino acid, readily prepared by hydrolysis of the corresponding hydantoin (Equation (2)), and remove the D-isomer by oxidation using d-AAO. 

One of the papiliochromes, papiliochrome II (142), isolated from Papilio butterflies, is actually a pair of optical isomers, papiliochromes Ila and lib. Compound 142 is hydrolyzed by treatment with 10 iV HCl to afford l-kynurenine and a new catecholamine (400) (71). Results of acid hydrolysis of the latter with 1 N HCl and the mass and C-NMR spectra suggest that the structure of 400 is iV-P-alanylnoradrenaline, which was proved by chemical synthesis. The C-NMR data indicate that papiliochrome II is represented as structure 142 in which the nitrogen of aromatic amino group of kynurenine is bonded to C-5 of the side chain ofiV-P-alanyldopamine. The existence of optical isomers, Ila and... 

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